The present invention relates to therapeutic methods for treatment of conditions related to glucosylceramide synthesis disorders, for example, Niemann-Pick C storage disease, Alzheimer""s disease, epilepsy, stroke, and Parkinson""s disease.
Niemann-Pick Type C (NPC) disease, also known as Niemann-Pick disease with cholesterol esterification block, is an autosomal recessive storage disorder of cholesterol metabolism. NPC patients generally appear normal for the first few years of life. However, organomagly of the liver and spleen soon emerge, and may result in jaundice or other symptoms of dysfunction. NPC patients also gradually develop neurologic abnormalities such as ataxia, tremors, seizures, and loss of speech, cognitive and motor skills, and difficulty with upward and downward eye movements. Impairment progresses, particularly resulting from increasing neural degeneration, and death usually occurs by 5-15 years of age.
Vanier et al. (1991) reported that Niemann-Pick Type C is heterogeneous, suggesting the possibility that more than one genetic mutation gives rise to the disease. Molecular studies recently substantiated this possibility. A gene most commonly mutated in Niemann-Pick Type C patients has been identified as NPC1 and mapped to 18q11-q12. The NPC1 gene encodes a protein of 1,278 amino acids, and bears some sequence homology to the putative sterol-sensing regions of SREBP cleavage-activating protein and 3-hydroxy-3-methylglutaryl coenzyme A reductase. A specific function for the NPC1 gene product is unknown at this time, although biochemical studies are suggestive that NPC1 gene mutations somehow disturbs cholesterol metabolism. For example, NPC cells are blocked in cholesterol esterification and do not effectively translocate cholesterol from lysosomes to other intracellular organelles.
Evidence for a second possible gene mutated in Niemann-Pick type C has been described, although it has not yet been identified. Patients with NPC1 mutations have been subclassified as having Niemann-Pick type C1 disease, while patients with other mutated gene(s) as having Niemann-Pick type C2 disease. There is no known difference between the clinical courses of type C1 and C2 patients, which appear to respond in the same way to disease treatments. In addition, the C1I/C2 subclassification is not universally applied. Therefore, Niemann-Pick Type C diseases originating from NPC1 or other gene mutations are collectively referred to as NPC here.
Biochemical findings for NPC patients show a marked accumulation of cholesterol in the liver and spleen, as well as elevated sphingomyelin levels. However, sphingomyelinase activity remains normal in these tissues. This finding distinguishes NPC from Niemann-Pick Types A and B diseases which are caused by lysosomal sphingomyelinase mutations, and exhibit markedly reduced levels of this enzyme.
In addition to the liver and the spleen, other cells of NPC patients store cholesterol as well. For example, bone marrow cells take on a characteristic foamy appearance due to the presence of large numbers of storage inclusions, while eye and skin cells typically are less affected. Neuronal cells store some cholesterol, although glycolipid accumulation predominates, particularly GM2 ganglioside. Affected neuronal cells in NPC patients undergo morphologic changes including the development of fibrillar tangles that are structurally similar to those seen in neurodegenerative disorders such as Alzheimer""s disease and tuberous sclerosis. The age of onset and the rapidity of neuronal deterioration in NPC patients can vary considerably. The mechanism underlying these neurologic changes is unknown. It has been proposed that elevated levels of GM2 may induce ectopic dendritic proliferation and meganeurite formation (Goodman and Walkley (1996) Brain Res Dev Brain Res 93:162-71). Dendritogenesis and neuron changes correlate well with disease severity in a feline model of NPC (March et al, 1997) Acta Neuropathol. 94:164-172).
There is as yet no accepted treatment for NPC disease. Given the observations supporting the origin of NPC disease in a cholesterol metabolism defect, most treatment attempts have focused on reducing cholesterol storage (Sylvain et al. (1994) Pediatr. Neurol. 10:228-32; Patterson et al (1993) Neurology 43:61-4). However, restricting cholesterol intake or treating patients with a range of cholesterol-lowering drugs has had puzzlingly little effect on the tissue storage levels of this material, and no apparent effect on the disease""s progress.
It is generally accepted that the glycolipid accumulation component of NPC disease is a secondary effect of the cholesterol metabolism defect component (see for example Chapter 85 in The Metabolic and Molecular Bases of Inherited Disease, 7th edition, McGraw-Hill Inc, New York, pp 2625-2639 (1995), Loftus et al. (1997) Science 277: 232-235). Thus, until now, little attention has focused on treating this component of the disease.
The imino sugar N-butyldeoxynojirimycin (NB-DNJ) is a potent inhibitor of alpha-glucosidase 1, an enzyme involved in N-glycan synthesis, and an even more potent inhibitor of glucosylceramide glucosyltransferase. NB-DNJ is currently undergoing clinical trials as a treatment for Gaucher and Fabry diseases, which are glycolipid storage disorders resulting from mutations in glucocerebrosidase and alpha-galactosidase A, respectively (see FIG. 1). The rationale underlying these clinical trials is based on the observation that cells treated with NB-DNJ produce markedly reduced glucosylceramide levels because of inhibition of glucosylceramide synthesis. Thus, the clinical trials are determining whether patient health benefits could be achieved by balancing a NB-DNJ induced decrease in the rate of glucosylceramide synthesis against the impaired rate of glycolipid clearance seen in Gaucher and Fabry disease patients. Methods and processes for the production of N-butyldeoxynojirimycin can be found for example in U.S. Pat. Nos. 4,182,767, 4,266,025, and 5,151,519; as well as EP-B-0012278 and EP-A-0624652, which publications are herein specifically incorporated by reference.
The present invention is based in part on the discovery that neuronal glycolipid storage seen in NPC patients is reduced by NB-DNJ treatment. As demonstrated in the experiments described below, NB-DNJ markedly reduces clinical and pathological symptoms in feline and murine models of NPC.
Accordingly, in a first aspect, the present invention provides a method of treating Niemann-Pick type C disease, comprising administering a therapeutically effective amount of an inhibitor of glucosylceramide synthesis. In one embodiment, the inhibitor is an imide sugar. In more specific embodiments, the imide sugar is N-butyldeoxynojirimycin, N-butyldeoxygalactonojirimycin, or N-nonyldeoxynojirimycin. In a more specific embodiment, the imide sugar is N-butyldeoxynojirimycin, which is a potent inhibitor of both alpha-glucosidase 1 and glucosylceramide glucosyltransferase. In another embodiment, the inhibitor of glucosylceramide synthesis is 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), D-threo-1-phenyl-2-decanoylamino-3 -morpholino-1-propanol and structurally related analogues thereof.
In another embodiment of the method of the invention, a nucleic acid encoding a peptide or protein inhibitor of glucosylceramide synthesis is administered, and in a related embodiment, an antisense sequence or catalytic RNA capable of interfering with the expression of an enzyme required for glucosylceramide synthesis (e.g. glucosylceramide synthase) is administered. In further embodiments, inhibition of glucosylceramide synthesis is achieved with a combination of these approaches, for example, administration of an imide sugar and an antisense molecule capable of interfering with the expression of an enzyme involved in glucosylceramide synthesis.
In a second aspect, the present invention provides a pharmaceutical composition comprising an inhibitor of glucosylceramide synthesis selected from the group of N-butyldeoxynojirimycin, N-butyldeoxygalactonojirimycin, N-nonyldeoxynojirimycin, 1-phenyl-2-decanoylamino-3-moipholino-1-propanol (PDMP), D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, and structurally related analogues thereof, and a pharmaceutically acceptable carrier.
In a third aspect, the invention provides a method of treating Niemann-Pick type C disease, comprising administering a therapeutically effective amount of an agent capable of increasing the rate of neuronal glycolipid degradation. In more specific embodiments, the agent is a neuronal glycolipid degrading enzyme, for example, a lysosomal hexoseaminidase, a galactosidase, a sialidase and glucosylceramide glucosidase. In further embodiments, the agent is a molecule which increases the activity of a glycolipid degrading enzyme. In still further embodiments, the agent is a nucleic acid sequence (DNA or RNA) which encodes a neuronal glycolipid degrading enzyme.
In a fourth aspect, the present invention provides a method of treating Alzheimer""s disease, comprising administering a therapeutically effective amount of an inhibitor of glucosylceramide synthesis. In one embodiment, the inhibitor of glucosylceramide synthesis is an imino sugar. In more specific embodiments, the imide sugar is N-butyldeoxynojirimycin, N-butyldeoxygalactonojirimycin, or N-nonyldeoxynojirimycin. In a more specific embodiment, the imide sugar is N-butyldeoxynojirimycin, which is a potent inhibitor of both alpha-glucosidase 1 and glucosylceramide glucosyltransferase. In another embodiment, the inhibitor of glucosylceramide synthesis is 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol and structurally related analogues thereof.
In a fifth aspect, the invention provides a method of treating Alzheimer""s disease, comprising administering a therapeutically effective amount of an agent capable of increasing the rate of neuronal glycolipid degradation. In more specific embodiments, the agent is a neuronal glycolipid degrading enzyme, for example, a lysosomal hexoseaminidase, a galactosidase, a sialidase and glucosylceramide glucosidase. In further embodiments, the agent is a molecule which increases the activity of a glycolipid degrading enzyme. In still further embodiments, the agent is a nucleic acid sequence (DNA or RNA) which encodes a neuronal glycolipid degrading enzyme.
In a sixth aspect, the present invention provides a method of treating or ameliorating epilepsy, comprising administering a therapeutically effective amount of an inhibitor of glucosylceramide synthesis. In one embodiment, the inhibitor of glucosylceramide synthesis is an imino sugar. In more specific embodiments, the imide sugar is N-butyldeoxynojirimycin, N-butyldeoxygalactonojirimycin, or N-nonyldeoxynojirimycin. In a more specific embodiment, the imide sugar is N-butyldeoxynojirimycin, which is a potent inhibitor of both alpha-glucosidase 1 and glucosylceramide glucosyltransferase. In another embodiment, the inhibitor of glucosylceramide synthesis is 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol and structurally related analogues thereof.
In a seventh aspect, the invention provides a method of treating or ameliorating epilepsy, comprising administering a therapeutically effective amount of an agent capable of increasing the rate of neuronal glycolipid degradation. In more specific embodiments, the agent is a neuronal glycolipid degrading enzyme, for example, a lysosomal hexoseaminidase, a galactosidase, a sialidase and glucosylceramide glucosidase. In further embodiments, the agent is a molecule which increases the activity of a glycolipid degrading enzyme. In still further embodiments, the agent is a nucleic acid sequence (DNA or RNA) which encodes a neuronal glycolipid degrading enzyme.
Preliminary clinical trials have shown that neurodegenerative processes seen with Parkinson""s disease, stroke and spinal cord injuries seem to improve by treating patients with GM1 ganglioside (Alter (1998) Ann N Y Acad Sci 845:391-4011; Schneider (1998) Ann N Y Acad Sci 845:363-73; Geisler (1998) Ann N Y Acad Sci 845: 374-81). Accordingly, in a separate eighth aspect, the invention features a method of modulating glucosylceramide synthesis in Parkinson""s disease, stroke, and spinal cord injuries, comprising administering a therapeutically effective amount of a ganglioside. In a specific embodiment, the ganglioside is GM1 ganglioside.
In a ninth aspect, the invention features a pharmaceutical composition comprising a ganglioside, useful for treatment of Parkinson""s disease, stroke, and spinal cord injuries, and a pharmaceutically acceptable carrier. In a more specific embodiment, the ganglioside is GM1 ganglioside.
In another embodiment, the pharmaceutical composition comprises an inhibitor of glucosylceramide synthesis and a ganglioside, useful for simultaneous, sequential or separate treatment in the treatment of a condition treatable by the administration of a ganglioside. In a more specific embodiment, the ganglioside is GM1 ganglioside. In one embodiment, the glucosylceramide synthesis inhibitor is an imino sugar. In more specific embodiments, the imide sugar is N-butyldeoxynojirimycin, N-butyldeoxygalactonojirimycin, or N-nonyldeoxynojirimycin. In another embodiment, the inhibitor of glucosylceramide synthesis is 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol and structurally related analogues thereof.
In another embodiment, the pharmaceutical composition comprises a therapeutically effective amount of an agent capable of increasing the rate of neuronal glycolipid degradation and a ganglioside. In a more specific embodiment, the ganglioside is GM1 ganglioside. In other specific embodiments, the agent is a neuronal glycolipid degrading enzyme, for example, a lysosomal hexoseaminidase, a galactosidase, a sialidase and glucosylceramide glucosidase. In further embodiments, the agent is a molecule which increases the activity of a glycolipid degrading enzyme. In still further embodiments, the agent is a nucleic acid sequence (DNA or RNA) which encodes a neuronal glycolipid degrading enzyme.
Other objects and advantages will become apparent from a review of the ensuing detailed description taken in conjunction with the following illustrative drawing.